Commercially available eye viewing devices for use in retinal viewing have been observed to exhibit numerous limitations.
According to an ophthalmoscope design, a beam splitter is provided in the optical viewing path which directs illumination light rays into an eye, and simultaneously allows receive imaging light rays to pass therethrough. The substantial light losses inherent with this design requires that a large, high powered light source be incorporated in the device for the device to satisfactorily illuminate a retina. High powered light sources, in general, are difficult to package, consume excessive amounts of electrical input power, and produce large amounts of heat and unwanted light such as glare. High powered light sources also have large filaments, typically larger than the diameter of an undilated pupil. This makes indirect ophthalmoscopes especially susceptible to glare problems attributable to incident light rays being reflected from outer eye structures such as the iris, cornea and sclera. Additionally, because there is a limit to the level of illumination which is safe to introduce into they eye, high powered illumination systems never fully compensate for the losses introduced by a beamsplitter.
Cameras for use in retinal viewing, such as fundus cameras, provide high quality imaging. However, retinal viewing cameras, in general, are expensive, typically require pupil dilation for retinal viewing, and typically require operation by a highly skilled and trained camera operator and these cameras are also large, bulky, and consume excessive space. Because present retinal viewing cameras are fixed position cameras, they require that a a patient move into a certain position relative to the camera for an operative position to be achieved. Further, they frequently illuminate with infrared illumination only during “aiming” which makes the views during aiming unsuitable for diagnosis.
There is a need for a compact, lower input power eye hand-held viewing device which provides appropriate retinal illumination, which facilitates wide field retinal viewing without requiring pupil dilation, and which can be adapted for use in producing both a suitable view for diagnosis and the capability of capturing images corresponding to eye structures.